Pressure Body Sliding Layer for Thermal Stress Reduction
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Solution Overview
Problem
The semiconductor industry faces challenges in bonding chips to substrates due to thermal expansion issues during the bonding process, which can lead to thermal stresses and inefficiencies in pressure transmission.
Innovation Solution
A pressure transmission apparatus with a sliding motion mechanism transverse to the bonding direction, utilizing a carbon-containing solid sliding layer and elastic fixing means, which decouples the pressure body from other components, allowing for frictionless motion and matching thermal expansion properties with the substrate and chips, and incorporating an elastic and hard layer for uniform pressure application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If chips and substrate are heated during bonding, then bonding temperature is achieved for permanent connection, but thermal expansion causes thermal stresses and bonding defects
Solution Approach 1:
The heating process is segmented into two distinct phases: (1) preliminary heating of substrate and chips to bonding temperature before pressure application, and (2) pressure application at constant temperature. This segmentation prevents thermal stresses during pressure transmission by completing thermal expansion before mechanical bonding begins.
Solution Approach 2:
The substrate and chips are preliminarily heated to the bonding temperature before the pressure body is applied. This preliminary thermal treatment ensures that thermal expansion occurs prior to pressure transmission, eliminating thermal stresses during the bonding pressure phase.
2Force
If pressure body is rigidly fixed during bonding, then stable bonding force is maintained, but thermal expansion mismatch causes stress and reduces bonding quality
Solution Approach 1:
The pressure body's thermal expansion coefficient is matched to that of the substrate through material selection and dimensional design. This parameter matching ensures that both components expand at the same rate during heating, preventing differential thermal stresses while maintaining stable bonding force.
Solution Approach 2:
The pressure body is constructed as a composite structure with specific material properties that match the substrate's thermal expansion characteristics. This composite design allows the pressure body to thermally expand in sync with the substrate, eliminating stress concentration at the interface.
3Area of stationary object
If pressure body dimensions are larger than substrate, then complete coverage is achieved, but edge overhang causes misalignment and bonding defects
Solution Approach 1:
The pressure body dimensions are locally optimized to match the substrate's active bonding area. The pressure body is designed with dimensions that correspond precisely to the chip array area on the substrate, providing uniform pressure distribution without edge overhang that could cause misalignment.
4Productivity
If heating is performed simultaneously with pressure application, then bonding process is completed in one step, but thermal stresses compromise bonding quality
Solution Approach 1:
The bonding process is segmented into two sequential steps: (1) heating substrate and chips to bonding temperature without pressure, and (2) applying pressure at constant temperature. This temporal segmentation ensures thermal expansion completes before pressure transmission, maintaining bonding quality while preserving overall process efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution minimizes scrap and optimizes the bonding process by reducing thermal stresses and ensuring uniform pressure application, enhancing the bonding efficiency and reducing thermal expansion-related issues.
Implementation Method 1
The sliding layer thus allows almost completely frictionless relative motion of the components bordering it
Implementation Method 2
the chips and the substrate are heated while the chips are being pressed onto the substrate (bonding force)... due to thermal expansion during heating
Implementation Method 3
the fixing means are made elastic transversely to the bonding direction B. Thus, at the same time the fixing means can provide for holding the pressure transmission apparatus together in the bonding direction B
Data Source
AI summary
This invention relates to a pressure transmission apparatus for bonding a plurality of chips to a substrate. The pressure transmission apparatus includes a pressure body for applying a bonding force which acts in the bonding direction (B) to the chip. The pressure body has a first pressure side and an opposite second pressure side, both oriented to be transverse to the bonding direction (B). Fixing means are provided to attach to the periphery of the pressure transmission apparatus for fixing of the pressure transmission apparatus on a retaining body in the bonding direction (B). A sliding layer is provided for sliding motion of the pressure body transversely to the bonding direction (B).